Lower levels of physical activity, an "unhealthy" diet and the presence of overweight/obesity are established risk factors for several types of cancer. There is a growing interest in exploring the potential links between environmental characteristics and chronic diseases, such as breast cancer in women. Previous research done by our group has demonstrated a link between neighborhood characteristics, such as walkability, and risk factors for chronic diseases. Therefore, using the San Diego cohort of the Women's Health Initiative (WHI), we propose to test the hypothesis that neighborhood characteristics would potentially moderate the association between common behavioral risk factors and incident breast, colorectal and total cancers. To do so, we propose to conduct a study employing the following specific aims: 1. To assess the baseline associations among the neighborhood environment factors (built, sociodemographic, and food) and common, behavioral cancer related risk factors (physical activity, diet, body mass index). 2. After adjustment for pertinent cancer risk factors, to determine the potential direct effects of the neighborhood environmental factors on incident cancer outcomes (breast, colorectal, total). 3. Using multivariable models, to ascertain the direct, mediated or moderated effects of both the neighborhood environment and cancer risk factors on incident cancer outcomes. Participants'neighborhood characteristics within a 1 kilometer buffer of their residence will be geocoded using geographic information systems (GIS) and linked to census, land use and business license data. This data will then be merged to the existing data from the San Diego WHI cohort, which includes extensive baseline characteristics (i.e. physical activity, dietary and body morphology measurements) as well as incident cancer events that were adjudicated using a standard protocol and central physician adjudicators. Once linked, appropriate analyses will be conducted to test the specific aims listed above. We believe the proposed study is innovative because of the prospective nature of the follow-up and it will test links between multiple neighborhood characteristics and not only cancer risk factors but multiple types of cancer. This research is important because it would extend the existing literature on neighborhood characteristics beyond common behavioral risk factors to incident cancers and it would inform and potentially influence theoretical models on the associations between neighborhood structure and cancer events. As such, this study could have implications for policy formulation on neighborhood design and development. PUBLIC HEALTH RELEVANCE: Lower levels of physical activity, an "unhealthy" diet and the presence of overweight/obesity are established risk factors for several types of cancer. There is a growing interest in determining if there are links between the environment in which one lives and chronic diseases, such as breast cancer in women. Therefore we propose to determine if the neighborhood environment influences the association between common behavioral risk factors and new breast, colorectal and total cancers.